Catalytic Behavior and In Situ X‐Ray Diffraction of Promoted Iron Catalysts for Fischer‐Tropsch Synthesis

The effects of structural promoters (ZnO, SiO 2 , and Al 2 O 3 ) on the phase transformation during reduction and Fischer‐Tropsch synthesis (FTS) of a FeCuK catalyst were investigated by in situ X‐ray diffraction and the FTS catalytic performance was studied in a fixed‐bed reactor. The reduction follows the path of Fe 2 O 3 /K 2 Fe 22 O 34 → Fe 3 O 4 → α ‐Fe. The addition of ZnO, SiO 2 , and Al 2 O 3 delayed and prolonged the reduction. The iron carbides formed under reaction conditions were χ ‐Fe 5 C 2 and ε ‐Fe 2 C. The presence of ZnO, SiO 2 , and Al 2 O 3 favored the formation of χ ‐Fe 5 C 2 . ε ‐Fe 2 C is a more active phase. Besides, ε ‐Fe 2 C seems to favor the formation of CO 2 and C 5+ and χ ‐Fe 5 C 2 benefits CH 4 and C 2 –C 4 products.